Oxidation op olefins to ketones



OXIDATION OF OLEFINS TO KETONES Filed Jan. 18, 1963 2 Sheets-Sheet 1 a OI FIG. 7.

1: A INVENTORS RICHARD NORMAN LACEY KENNETH ALLISON ATTORNEYS June 28, 1966 R. N. LACEY ETAL OXIDATION OF OLEFINS TO KETONES 2 Sheets-Sheet 2 Filed Jan. 18, 1963 E g @T ,3

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RICHARD NORMAN LACEY KENNETH ALLISON flit/Z 4? I" ATTORNEYS United States Patent 3,258,491 OXIDATION OF OLEFINS T0 KETONES Richard Norman Lacey and Kenneth Allison, Sunburyon-Thames, Middlesex, England, assignors to The British Petroleum Company Limited, London, England,

a British joint-stock corporation Filed Jan. 18, 1963, Ser. No. 252,375 Claims priority, application (jrezat Britain, Feb. 9, 1962,

7 Claims. (Cl. 26tl5%) This invention relates to a process for the oxidation of olefinic hydrocarbons and more particularly it relates to the production and recovery of ketones from olefins by the oxidation thereof.

It is Well known that the oxidation of olefins with molecular oxygen produces a mixture of oxy-compounds which include unsaturated hydroperoxides, ketones, aldehydes, alcohols and olefin oxides. By subsequent hydrogenation and dehydrogenation steps it is known that the unsaturated ketones and alcohols present may be converted to saturated ketones which have utility as solvents. In such a process the yields of saturated ketones are unacceptably low to make the process economic on the commercial scale. This is due in part to the low degree of oxidation experienced per pass resulting in the formation of a crude oxidate containing substantial amounts of unreacted olefin, and in part to the presence in the oxidate of oXy-compounds which do not yield saturated ketones in the hydrogenation and l dehydrogenation stages.

It is an object of the present invention to maximise the yields of saturated ketones obtainable from olefins by the initial oxidation thereof and to provide 'a continuous process whereby such yields may be obtained.

Accordingly the present invention provides a process for the preparation of saturated ketones from olefins having the formula R (R )C=C(H)R where R is hydrogen or an alkyl group and R and R are alkyl groups which comprise oxidising the olefin in the presence of molecular oxygen, separating unreacted olefin from the crude oxidate, subjecting the oxy-compounds produced .to hydrogenation, treating the hydrogenation products under acid conditions, recovering from the products of said treatment a fraction consisting essentially of olefins for recycle to the, oxidation stage and a fraction consisting essentially of oxy-compounds which is dehydrogenated to produce a product consisting essentially of saturated ketones.

The olefin feedstock for the present invention may consist of a pure olefin of the above formula or a mixture of such olefins. consist of an olefin or olefins of the above formula together with other mono-olefins. Suitable olefins are 2-methylbutene-2, 2-methylpentene-2, 2-methylhexene-2 or 2,3-dimethylpentene-2 or mixtures thereof.

Preferably the olefin feedstock will consist of methylpentenes, e.g. 2-rnethylpentene-2 and/ or 4-methylpentene- 2. Mixed methylpentenes obtained from the dimerisation of propylene over suitable catalysts, for example, sodium on a potassium carbonate support or an alkali metal/graphite complex catalyst, describedin pending United States patent applications, Serial Nos. 95,801, 95,802 and 160,625 and United States Patents Nos. 3,084,206 and 3,190,937 respectively, are suitable feedstocks. Such mixed methylpentenes may be treated to separate isomers not conforming to the formula set out above, e.g. 4-methylpentene-l, or subjected to isomerisation to enhance the concentration of methylpentenes conforming to the above formula, prior to use in the present invention.

The oxidation reaction may be carried out in either The feedstock may also suitably the liquid or vapour phase and with or without the assistance of oxidation catalysts such as salts of heavy metals of Group VIII of the Periodic Table. Suitably the oxidation is carried out in the liquid phase at temperatures little above ambients, e.g. 40 C. to 55 C. in the presence of a cobalt catalyst, e.g. cobalt naphthenate.

The product of such oxidation isa complex mixture of oxy-compounds together with some unreacted olefin. The oxy-compounds will include unsaturated hydroperoxides, ketones, aldehydes and alcohols, together with epoxides..

From the crude oxidate, the unreacted olefin is separated This may be carried out by low temperature distillation but such an operation may behazardous due to the need to handle a bottom product in which the relatively unstable unsaturated hydroperoxides are concentrated. Conveniently the olefin separation may be carried out at reduced pressure in the presence of an added inert diluent liquid which boils between the boiling point of the olefin and the boiling point of. the lowest boiling oxy-product. Such a separation process has been described in pending United States patent application, Serial No. 256,513. The diluent may be recovered in a later stage and recycled.

A further suitable means for separating the unreacted olefin from the oxy-products is to subject the crude oxidate to a selective hydrogenation step in which the unstable unsaturated hydroperoxides present are selectively reduced to stable unsaturated alcohols. The product of such selective hydrogenation may then be distilled in a conventional manner to recover unreacted olefin and the oxy-cornpounds recovered as bottom product passed to the hydrogenation stage. Suitable selec tive hydrogenation catalysts that may be employed are those described in pending United States patent application, Serial No. 247,862, e.g. leador mercury poisoned palladium supported on calcium carbonate.

The olefin recovered from the crude oxidate is recycled to the system. Thus it may be recycled directly to the oxidation stage or the feed prior to entering the oxidation stage. The unreacted olefin recovered may, depending on the composition of the feed, contain olefins not readily susceptible to oxidation and continuous recycle of such olefins would eventually lead to an undesirable build up. In. such circumstances it is desirable to subject at least a portion of these olefins to an isomerisation step wherein there is produced an equilibrium mixture predominating in olefins of the formula set out above. As an example of this feature there may be quoted the instance where the feed olefin is a mixture containing Z-methylpentene-Z and 2-methylpentene-l. The later is far less susceptible to oxidation than the former and therefore its relative concentration in the olefin mixture recovered from the oxidate is increased. It is therefore desirable to isomerise such an olefin mixture in order to convert at least some of the Z-methylpentene-l to Z-methylpentene-Z before recycle to the oxidation stage. This may be effected under acid conditions for example under conditions analogous to those used to treat the hydrogenation products in the process scheme. Thus, such isomerisation may be effected in. the zone used for acid treatment of the hydrogenation products or in a separate zone.

A portion of the recycle stream may be purged if desired to avoid the build up of relatively unreactive olefins.

The oxidate from which the unreacted olefin has been stripped is then hydrogenated using any conventional method for example using a nickel hydrogenation catalyst. In this stage the unsaturated oxy-compounds are hydrogenated to the corresponding saturated compounds any epoxides present remaining unchanged.

acid. The operating conditions, e.g. pressure, temperature and contact time will vary according to the reactants used. Suitably for alumina the temperature would be about 300 C. whilst for aqueous sulphuric acid, it could vary between ambient and boiling point, depending on the concentration of acid used. 'By the acid treatment, epoxides are converted to ketones and alcohols are dehydrated to produce olefins. Also any olefins isomeric with the feed olefin produced by dehydration will be isomerized to yield an equilibrium mixture predominating in olefins of the R (R )C=C(H)R type under the conditions prevailing during the acid treatment. Preferably conditions are chosen for the acid treatment such that only tertiary alcohol and substantially no secondary alcohols present in the hydrogenated products are dehydrated to olefin. Suitable acid treatments to achieve such selectivity are the use of aqueous sulphuric'or phosphoric acid of up to 40% by weight concentration at temperatures of at least 50 C., generally up to about 200 C., or treatment in the vapour phase with dehydrating catalysts such as activated alumina or phosphoric acid on pumice at temperatures of at least 50 C., generally in the range 50 to 300 C., e.g. 200 C. The products from the acid treating zone are separated, conveniently by distillation, into a fraction consisting essentially of oxy-compounds and a fraction consisting essentially of olefins. At least a portion of the olefinic fraction is recycled to oxidation.

It may be desirable to further separate the olefinic fraction before recycle since it will invariably contain some olefins not readily susceptible to oxidation. For example, it may be desirable to separate the olefins into a fraction consisting essentially of olefins of the type, as hereinbefore defined, and into a fraction containing little of such olefins. This latter fraction may be removed from the process scheme or recycled to the acid treatment zone wherein it will undergo isomerisation.

Preferably the hydrogenation products are treated under acid conditions whereby an overhead product consisting of olefins is continuously removed from the acid treatment zone and recycled to the oxidation stage and the bottom product which is a mixture of oxy-compounds containing mainly saturated ketones and secondary alcohols is dehydrogenated.

The dehydrogenation step may be any conventional one known in the art. A suitable stepemploys a copper, zinc oxide catalyst supported on pumice at temperatures in the range 250 to 450 C. Hydrogen liberated may be recycled to the hydrogenation step.

The product from the hydrogenation is a mixture of oxycompounds containing a high proportion of saturated ketones. These ketones may be recovered in a substantially pure form by distilling the dehydrogenation products and removing the ketone fraction overhead, a small amount of high boiling material being recovered as bottom product. The ketone fraction may be contaminated with small amounts of close boiling aldehydes which may be removed by suitable treatment such as by oxidation in the presence of a catalyst such as cobalt naphthenate to form products easily separated from the ketone by distillation, or by acetal formation which again produces a product easily distilled from the ketone.

The weight yield of ketones obtained expressed as a percentage of reached olefin in the initial feed is in the region of 95%.

. The invention will now -be described having regard to the embodiment illustrated in the accompanying drawings in which FIGURE 1 and FIGURE 2 represent schematic flow schemes for embodiments of the invention.

FIGURE 1 illustrates schematically, a flow scheme for an embodiment of the present invention using, as feedsock, a mixture of methylpentenes having an approximate composition:

Percent 4-methylpentene-2 52 2-methylpentene-2 13 2-methylpentene-1 30 4-methylpentene-1 5 The methylpentene mixture is passed via line 11 into an oxidation zone 1 wherein it is reacted with air in the liquid phase at a temperature of about 45 C. in the presence of a cobalt naphthenate catalyst. The oxidation product is led through line 12 to a separation unit 2 wherein oxy-cornpounds are separated from unreacted olefin and led via line 13 to a hydrogenation zone 3. The hydrogenation product is passed through line 15 together with unreacted olefin from overhead line 14 into an acid treating zone 4 wherein the mixture is treated with hot 20% aqueous sulphuric acid.

In an alternative procedure not illustrated, the olefin in line 14 is fed to an acid treating zone separate from zone 4 without combining streams in lines 14 and 15. The acid treated products from the two zones may be separately fed to column 5, or may be combined before being fed to this column.

The acid treated product is then passed through line 16 to a distillation column 5 wherein it is separated into an olefin fraction and an oxy-compound fraction which is predominantly a mixture of secondary alcohols and ketones which is recovered via line 19 and is then dehydrogenated by conventional means not shown to form a product consisting essentially of ketones. The olefin fraction is further fractionated to remove 4-methylpentene-l through line 18, the remaining olefin comprising a mixture of 2-methylpentene-1 and 2-methylpentene-Z, predominantly the latter, is recycled to oxidation.

It will be appreciated that there are many variations on the illustrated flow scheme shown in FIGURE 1 depending on the feedstock used. For example if a pure 2-methylpentene-Z were used as feedstock, unconverted olefin separated in colum 2 could be returneddirectly to oxidation. The olefin from the acid treating zone 4 removed from column 5 via line 15, would consist in this case essentially of an equilibrium mixture of about 2 methylpentene-2 and 10% 2-methylpentene-1 and could be separated by distillation into a fraction rich in 2-methylpentene-Zand are rich in 2-methylpentene-1. The for- Percent 4-methylpentene-2 64.4 Z-methylpentene-Z 14.0 2-methylpentene-1 3.4

Rest mainly 4-methylpentene-1 and methylpentanes 18.2

The feed stream is fed by line 111 into an oxidation zone 101 Where it is oxidised in the presence of 0.2 g./l. cobalt naphthenate in the presence of air at a temperature of about 75 C. and a pressure of p.s.i.g. Air is introduced through line 128. Olefin residence time in the reactor is 7.2 hours. The crude oxidate containing unreacted olefin and a mixture of oxy-products is passed to an olefin stripper 102 wherein the oxidate is distilled at reduced pressure in the presence of benzene. The conditions in this zone are a pressure of 239 mm. Hg; a reflux temperature of 33 C.; and a reflux ratio of 3:1. The olefin is recovered overhead and fed by line 114 to an isomerisation zone wherein a certain amount of the Z-methyIpentene-l present is isomerised to 2- methylpentene-2 in the presence of 20% wt. aqueous sulphuric acid and at a temperature of 65 C. and at atmospheric pressure and the product stream is recycled to the feed. A portion of the olefin recovered in'the stripper may be purged through line 114A, if desired. The oxy-products and benzene recovered from the olefin stripper are led through line 113 to a hydrogenation zone 103 and the hydrogenated products are then fed to a benzene stripper 105 wherein benzene is recovered overhead for recycle in line 117. The hydrogenation is carried out in the presence of 1.45% wt. of a catalyst which is palladium supported on pumice at a temperature of 87 C.; atmospheric pressure; a hydrogen feed rate of 100 v./v./hr. and a liquid feed rate of 0.75 v./v./hr. The hydrogenated oxy-products recovered as bottoms in the benzene stripper are passed to an acid treating zone 104 wherein they are treated with 20% aqueous sulphuric acid under reflux at atmospheric pressure. In this zone the 2-methylpentanol-2 present is dehydrated to an equilibrium mixture of 2-methylpentene-2 and Z-methylpentene- 1, and the methylpentene oxides present are rearranged to a mixture of ethyl, isopropyl ketone and methyl isobutyl ketone plus a small amount of aldehydes and high boiling material. The olefins produced are continuously recovered overhead and recycled through line 119. The oxy-products containing predominantly methyl isobutyl and ethyl isopropyl ketones and carbinols are fed via line 118 to a dehydrogenation zone 106 wherein the carbinols are convertedto the corresponding ketones, in the presence of a catalyst comprising nickel and zinc oxide supported on pumice, at a temperature of 320 C., atmospheric pressure, and a liquid feed rate of 1.9 v./v./hr. Hydrogen liberated is recovered and recycled in line 121 to the hydrogenation zone to which more hydrogen is added through line 129.

The product from the dehydrogenation zone are fractionated in columns 107 and 108, the ketones together with a small amount of aldehydes arerecovered via line 123 and fed to an aldehyde separation zone 109 from which a mixture of substantially pure methyl isobutyl ketone and ethyl isopropyl ketone are recovered.

The bottom product of fractionator 107 contains the high boiling constituents together with some methyl isobutyl and ethyl isopropyl carbinols which are stripped in fractionator 108 and recycled in line 125. I

In this process scheme, for every 100 parts by weight of olefin reacted, there is obtained, approximately 94 parts by Weight of the mixed ketones.

We claim:

1. In a process for the preparation of saturated ketones from olefins having the. formula R (R )C C(H)R where R is selected from the group consisting of a hydrogen atom and an alkyl group, and where R and R are alkyl groups, the steps comprisingi oxidizing the olefin in an oxidation stage in the liquid phase with molecular oxygen in the presence of a catalyst selected from the group consisting of salts of the heavy metals of Group VIII of the Periodic Table to form an oxidation products mixture of unreacted olefin and oxygenated products thereof; fractionally separating the oxidation products into a fraction consisting essentially of unreacted olefin and a fraction consisting essentially of oxygenated products of said olefin; hydrogenating said fraction consisting essentially of said oxygenated products in the presence of a catalyst selected from the group consisting of nickel hydrogenation catalysts and palladium supported on pumice whereby the unsaturated oxy-compounds are converted to the corresponding saturated oxycompounds; subjectingthe products of said hydrogenation to an acid treatment comprising contacting the hydrogenation products at a temperature of at least 50 C. with a material selected from the group consisting of (a) aqueous sulphuric acid, (b) aqueous phosphoric acid, said sulphuric and phosphoric acids being of up to 40% by weight concentration, (c) activated alumina, and (d) phosphoric acid supported on pumice; recovering from the products of said acid treatment a fraction consisting essentially of olefins for recycle to the oxidation stage and a fraction consisting essentially of oxy-compounds; and thereafter dehydrogenating the said oxy-compound fraction recovered from the products of said acid treatment in the presence of a catalyst selected from the group consisting of copper and zinc oxide supported on pumice and nickel and zinc oxide supported on pumice to produce a product consisting essentially of saturated ketones.

2. A process according to claim 1, wherein unreacted olefin is separated from the oxidation products by distillation at reduced pressure in the presence of an inert liquid diluent boiling between the boiling point of the highest boiling olefin and the lowest boiling oxy-compound present.

23. A process according to claim 1, wherein the unreacted olefin is separated from the oxidation products by subjecting the total oxidate to selective hydrogenations whereby unsaturated hydroperoxides present are selectively reduced to unsaturated alcohols and thereafter distilling ofl unreacted olefin.

4. A process according to claim 1, wherein the unreacted olefin separated is recycled to the oxidation stage.

5. A process according to claim 1, wherein the hydrogenated oxy-compounds are subjected to acid treatment in a reaction zone from which olefins are continuously removed overhead and recycled to the oxidation stage.

6. A process according to claim 1, wherein the feed olefin is methylpentene-Z.

7. A process according to claim 6, wherein the feed olefin is selected from the group consisting of Z-methylpentene-2 and 4-methylpentene-2 and wherein the product produced consists essentially of a mixture of methvlisobutyl ketone and ethylisopropyl ketone.

- References Cited by the Examiner UNITED STATES PATENTS 2,392,316 1/ 1946 Dreyfus 260451 2,580,528 1/ 1952 Dice et a1. 2,586,694 2/1952 Mottern 260596 FOREIGN PATENTS 448,177 4/ 1948 Canada. 1,111,124 10/1955 France.

662,575 12/ 1951 Great Britain. 668,931 3 /1952 Great Britain.

LEON ZITVER, Primary Examiner.

BERNARD HELFIN, Examiner.

D. HORWITZ, Assistant Examiner. 

1. IN A PROCESS FOR THE PREPARATION OF SATURATED KETONES FROM OLEFINS HAVING THE FORMULA R1(R2)C=C(H)R3, WHERE R1 IS SELECTED FROM THE GROUP CONSISTING OF A HYDROGEN ATOM AND AN ALKYL GROUP, AND WHERE R2 AND R3 ARE ALKYL GROUPS, THE STEPS COMPRISING: OXIDIZING THE OLEFIN IN AN OXIDATION STAGE IN THE LIQUID PHASE WITH MOLECULAR OXYGEN IN THE PRESENCE OF A CATALYST SELECTED FROM THE GROUP CONSISTING OF SALTS OF THE HEAVY METALS OF GROUP VIII OF THE PERIODIC TABLE TO FORM AN OXIDATION PRODUCTS MIXTURE OF UNREACTED OLEFIN AND OXYGENATED PRODUCTS THEREOF; FRACTIONALLY SEPARATING THE OXIDATION PRODUCTS INTO A FRACTION CONSISTING ESSENTIALLY OF UNREACTED OLEFIN AND A FRACTION CONSISTING ESSENTIALLY OF OXYGENATED PRODUCTS OF SAID OLEFIN; HYDROGENATING SAID FRACTION CONSISTING ESSENTIALLY OF SAID OXYGENATED PRODUCTS IN THE PRESENCE OF A CATALYST SELECTED FROM THE GROUP CONSISTING OF NICKEL HYDROGENATION CATALYSTS AND PALLADIUM SUPPORTED ON PUMICE WHEREBY THE UNSATURATED OXY-COMPOUNDS ARE CONVERTED TO THE CORRESPONDING SATURATED OXYCOMPOUNDS; SUBJECTING THE PRODUCTS OF SAID HYDROGENATION TO AN ACID TREATMENT COMPRISING CONTACTING THE HYDROGENATION PRODUCTS AT A TEMPERATURE OF AT LEAST 50*C. WITH A MATERIAL SELECTED FROM THE GROUP CONSISTING OF (A) AQUEOUS SULPHURIC ACID, (B) AQUEOUS PHOSPHORIC ACID, SAID SULPHURIC AND PHOSPHORIC ACIDS BEING OF UP TO 40% BY WEIGHT CONCENTRATION, (C) ACTIVATED ALUMINA, AND (D) PHOSPHORIC ACID SUPPORTED ON PUMICE; RECOVERING FROM THE PRODUCTS OF SAID ACID TREATMENT A FRACTION CONSISTING ESSENTIALLY OF OLEFINS FOR RECYCLE TO THE OXIDATION STAGE AND A FRACTION CONSISTING ESSENTIALLY OF OXY-COMPOUNDS; AND THEREAFTER DEHYDROGENATING THE SAID OXY-COMPOUND FRACTION RECOVERED FROM THE PRODUCTS OF SAID ACID TREATMENT IN THE PRESENCE OF A CATALYST SELECTED FROM THE GROUP CONSISTING OF COPPER AND ZINC OXIDE SUPPORTED ON PUMICE AND NICKEL AND ZINC OXIDE SUPPORTED ON PUMICE TO PRODUCE A PRODUCT CONSISTING ESSENTIALLY OF SATURATED KETONES. 